Systems and methods for sensing the surroundings of a vehicle

ABSTRACT

Systems and methods for sensing the surroundings of vehicles via vehicle mounted radar sensors. A directional transmitter array transmits radiation into the region surrounding the vehicle and a receiver array receives the radiation reflected back. Controllers may use self-velocity calculation modules, wall detection modules, dynamic range enhancement modules, double reflection detection modules and the like to harvest useful information such as the vehicles relative speed and the identification of hazards in its surroundings.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Pat. Application No.17/775,325 which was filed on May 9, 2022 as a U.S. National PhaseApplication under 35 U.S.C. 371 of International Application No.PCT/IB2020/060508, which has an international filing date of Nov. 9,2020 and which itself claims the benefit of priority from U.S.Provisional Pat. Application No. 62/932,511, filed Nov. 8, 2019, U.S.Provisional Pat. Application No. 62/955,487, filed Dec. 31, 2019, U.S.Provisional Pat. Application No. 63/037,021, filed Jun. 10, 2020, andU.S. Provisional Pat. Application No. 63/037,026, filed Jun. 10, 2020the contents of which are incorporated by reference in their entirety.

FIELD OF THE DISCLOSURE

The disclosure herein relates to systems and methods for sensing thesurroundings of vehicles. In particular systems and methods aredescribed for providing vehicle mounted radar sensors operable to detectobjects in the region surrounding a moving vehicle.

BACKGROUND

Various sensors may be used to sense objects. Indeed with the increasedusage of autonomous vehicles such as self-driving cars and the like aplethora of sensors are used to detect objects in the vicinity oftravelling vehicles. For example, sensors such as video cameras,ultrasonic sensors, infrared, LIDAR sensors and the like may be used toprovide information pertaining to the environment through which thevehicle is travelling.

The application of radar is becoming more and more popular with thedevelopment of the RFIC and signal technology. Radar sensors have theadvantage of operating in total darkness, fog, mist and rain. Radar isan electronic system with the advantages of low cost, low-powerconsumption, and high precision. It can be significantly applied invarious applications including, space shuttle topographic missions,optics, geotechnical mapping, meteorological detection, and so on. Theworking efficiency of a radar system is based upon reliable and stableradar signal with wide coverage, high directionality, high gain and lowsignal-to-noise ratio.

The usefulness of radars as vehicle mounted sensors depends upon theirresolution and accuracy of determining direction, range and speed. Thedirectionality achievable by antenna depends on its physical size,relative to the wavelength at the frequency of operation. This is truefor both mechanically steered and electronically steered beams.Electronic beam steering involves aligning the phases of signals from/toantenna elements in a given direction. The beam shape of an antennaarray depends upon the phase shift applied to each antenna element inthe array. Typically each antenna element has an a-priori implementationdependent phase shift related to the transmission lines and amplifiersalong the signal path to the antenna element. Where no additional phaseshift is applied, the resulting beam typically has no well-defined beamshape, such that the direction from which reflected beams are receivedis difficult to determine.

A well-known method of achieving highly directional beams is applyingphase shift along each path to the corresponding antenna elements, sothat the transmissions from different elements combine coherently in agiven propagation direction. However, applying arbitrary phase shiftincurs implementation complexity, and sometimes there’s a need to resortto coarse phase control. Examples of coarse phase control are selectingone of 2 or 4 possible phases, while finer control may allow selectingon of 8 or 16 phase values in each phase-controlled path.

Directionality to a transmitted beam may me achieved through binaryphase shift keying (BPSK) based beam forming. This may be achieved byapplying a 0-or-180 degree phase shift to the signal transmitted viaselected antennas. However, BPSK beamforming carrier a penalty due tothe coarse phase quantization and large difference, on the average,between the optimal desired and the actual phase. BPSK beam forminggenerates, on the average, significant side lobes which may dissipateabout 60% of the energy of the transmission. Reduction of sidelobescalls for finer-grain control of the phase, e.g. every 90 degrees ratherthan 180 degrees. With 90 degree granularity of phase control, only 20%of energy is lost to sidelobes.

By way of example, in the context of imaging, the transmit antennas maybe scanned by various code-sequences over several time intervals (forexample, switching between antennas over time, or coding the antennas bya Hadamard code, or beamforming toward specific directions). Thedirectional characteristics can be reconstructed by a-posterioribeamforming, combined with inversion of the encoding matrix. Reflectionfrom a moving target may produce phase rotation over those timeintervals in a manner detrimental to imaging. The motivation to generategood beamformers arrives from the fact that concentrating energy to adifferent direction in each time interval reduces the effect of phaserotation. Furthermore, where transmission sweep over a range offrequencies is transmitted over a time period, such as an up-chirp or adown-chirp, the delay between time intervals is increased still further.

As a result it can be very difficult to accurately determine thelocation of a target.

The need remains, therefore, for effective radar sensors which may beused to accurately sense objects in the region surrounding a travellingvehicle. The invention described herein addresses the above-describedneeds.

SUMMARY OF THE EMBODIMENTS

According to one aspect of the presently disclosed subject matter, asystem is introduced for sensing the surroundings of a vehicle. Thesystem may comprise a vehicle mounted radar unit including a radartransmission unit comprising an array of transmitter antennas connectedto an oscillator and configured to transmit electromagnetic waves into aregion surrounding the vehicle, and a radar receiving unit comprising atleast one receiver antenna configured to receive electromagnetic wavesreflected by objects within the region surrounding the vehicle andoperable to generate raw data.

The system may further include a processor unit in communication withthe radar receiving unit and configured to receive raw data from theradar unit and operable to generate environmental information based uponthe received data.

As required, the processor may comprises various additional modules suchas: a self-velocity calculation module operable to calculate velocity ofthe vehicle from raw data; a wall detection module operable to detectplanar surfaces in the region surrounding the vehicle; a dynamic-rangeenhancement module operable to distinguish objects reflecting weaklyfrom objects reflecting strongly within the same vicinity; and adouble-reflection identification module operable to distinguishsingle-reflected electromagnetic waves reflected directly by objectstowards the radar receiving unit from double-reflected electromagneticwaves reflected indirectly from objects towards the radar receiving unitvia intermediate reflective surfaces.

In some systems, the radar transmission unit further comprises apolarizer configured and operable to generate circularly polarizedelectromagnetic waves and/or the radar receiving unit further comprisesa polarization detector configured and operable to detect thepolarization of the received electromagnetic waves. Accordingly, thedouble-reflection identification module may comprise a circularpolarizer and a polarization detector.

Where required, the system includes a self-velocity calculation modulecomprising an image generation unit and a memory unit. The imagegeneration unit may be configured and operable to construct aconstructing a three dimensional image representing the regionsurrounding the vehicle comprising a matrix of voxels, each voxelcharacterized by a set of voxel parameters including: a horizontalspatial coordinate, x, of a reflecting object along an axis parallel tothe path of the vehicle; a vertical spatial coordinate, y, of thereflecting object along a vertical axis orthogonal to the path of thevehicle; a radial spatial coordinate, R, of the reflecting object alongan axis diverging radially from the vehicle; an intensity value; and aDoppler-shift value indicating an apparent radial velocity v_(R) of thereflecting object. The memory unit may be configured to store datapertaining to at least: a first three dimensional image representing theregion surrounding the vehicle at a first instant, and a second threedimensional image representing the region surrounding the vehicle at asecond instant after a delay time, dt.

Additionally or alternatively, the system may include a wall detectionmodule comprises a processing unit, and a memory unit storing executablecode directed towards comparing energy-profile within a virtual box witha reference energy-profile indicative of a two dimensional reflector.

Accordingly, it is another aspect of the disclosure to teach a methodfor sensing the surroundings of a vehicle by providing a vehicle mountedradar unit comprising a radar transmission unit comprising an array oftransmitter antennas connected to an oscillator, and a radar receivingunit comprising at least one receiver antenna; providing a processorunit in communication with the radar receiving unit; transmittingelectromagnetic radiation into the region surrounding the vehicle;receiving electromagnetic radiation reflected from an object in theregion surrounding the vehicle; detecting polarization of receivedelectromagnetic waves; detecting two dimensional extended targets withinthe region surrounding the vehicle; distinguishing objects reflectingweakly from objects reflecting strongly within the same vicinity byapplying dynamic-range enhancement filter combinations; constructing aseries of three dimensional images of the region surrounding thevehicle; and analyzing the series of three dimensional images todetermine the velocity of the vehicle.

Where appropriate, the step of detecting two dimensional extendedtargets in the region surrounding a vehicle may comprise: detecting aspectral-reflection point in reflected radiation; constructing virtualbox around volume containing a candidate wall-object; calculatingenergy-profile for the radar image within the virtual box; and applyinga classification function to the energy-profile.

Additionally or alternatively, the method may include applying aclassification function comprises calculating at least onewall-indication parameter selected from a group consisting of: overallenergy reflected from within virtual box; profile of reflected energyfrom within virtual box segments; number of voxels within virtual boxhaving energy values above a threshold value; and combinations thereof.

Where required, the step of constructing a series of three dimensionalimages comprises: constructing at least a first three dimensional imagerepresenting the region surrounding the vehicle at a first instant;waiting for a delay time, dt; and constructing a second threedimensional image representing the region surrounding the vehicle at asecond instant.

Accordingly, the step of analyzing the series of three dimensionalimages to determine the velocity of the vehicle may comprise: detectingcommon reflecting objects in the first three dimensional image and thesecond three dimensional image; determining a horizontal shift, dx, fordetected common reflecting objects; and calculating a gradient of a plotof apparent radial velocity vR as a function of horizontal shift dx forthe reflecting objects. Where appropriate, the step of determining thehorizontal shift, dx, comprises: determining an x-coordinate, xn, forthe reflecting object; determining a y-coordinate, yn, for thereflecting object; finding the reflecting object’s co-altitude angle,θn, by calculating the arctangent of the ratio (xn/yn) of thex-coordinate of the reflecting object and the y-coordinate of thereflecting object an angle; and calculating the sine of the co-altitudeangel such that dx=sin(arctan(xn/yn).

In still another aspect a method is taught for simulating quadraturephase-shift key (QPSK) beam forming in an antenna array, wherein eachantenna of the array is connected to a common transmitter via a binaryphase shifter. The method may include determining a required complexQPSK steering vector for each transmitting antenna of the array. Thesteering vector typically has a real component selected from 0 and 180degrees and an imaginary component selected from 90 and 270 degrees.

Accordingly, the transmitter generates an oscillating signal. During afirst time interval, for each transmitting antenna having an associatedsteering vector with a real component of 180 degrees, said binary phaseshifter a 180 degree phase shift to the transmitted signal is applied.During a second time interval, for each transmitting antenna having anassociated steering vector with an imaginary component of 180 degrees,said binary phase shifter a 180 degree phase shift to the transmittedsignal is applied. A post processor may be used to apply a 90 degreephase shift to signals received during the second time interval, and thepost processor may sum the signals received during the first timeinterval to 90 degree phase shifted signals received during the secondtime interval. Optionally the transmitter may sweep the oscillatingsignal over a range of frequencies during each time interval.

BRIEF DESCRIPTION OF THE FIGURES

For a better understanding of the embodiments and to show how it may becarried into effect, reference will now be made, purely by way ofexample, to the accompanying drawings.

With specific reference now to the drawings in detail, it is stressedthat the particulars shown are by way of example and for purposes ofillustrative discussion of selected embodiments only, and are presentedin the cause of providing what is believed to be the most useful andreadily understood description of the principles and conceptual aspects.In this regard, no attempt is made to show structural details in moredetail than is necessary for a fundamental understanding; thedescription taken with the drawings making apparent to those skilled inthe art how the various selected embodiments may be put into practice.In the accompanying drawings:

FIG. 1A schematically represents a vehicle mounted radar unit configuredto sense objects in the region surrounding a vehicle;

FIG. 1B is a block diagram indicating selected elements of a possiblesystem for sensing the surroundings of a vehicle;

FIGS. 2A-C are flowcharts indicating selected steps in possible methodsfor sensing the surroundings of a vehicle;

FIGS. 3A-D schematically represent a radar unit of the disclosuremounted to a moving vehicle detecting apparent movement of objects inthe region surrounding the vehicle;

FIGS. 4A-C are three examples of plots of apparent radial velocity v_(R)as a function of horizontal shift dx for the reflecting objects asmeasured by radar units mounted to vehicles travelling at differentspeeds;

FIG. 5 schematically represents a radar unit of the disclosure mountedto a moving vehicle detecting a wall-type two dimensional extendedtarget in the region surrounding the vehicle;

FIG. 6A illustrates how a steering vector may be generated by BPSK phaseshifting of the phase of selected antennas by 0 or 180 degrees;

FIG. 6B illustrates a possible BPSK mechanism for phase shifting thesignal to an antenna by 180 degrees;

FIG. 6C illustrates how a steering vector may be generated by QPSK phaseshifting of the phase of selected antennas by 0, 90, 180 or 270 degrees;

FIG. 6D illustrates a possible quadrature modulation mechanism for phaseshifting the signal to an antenna by 0, 90, 180 or 270 degrees;

FIG. 7A is a block diagram schematically representing selected elementsof a first embodiment of a system for simulating quadrature phase-shiftkeying (QPSK) beam forming;

FIG. 7B are a set of graphs indicating a possible set of profilesshowing an example of how the phase of the transmitted signal from eachtransmitter antenna of the first embodiment may change over time;

FIG. 7C is a flowchart indicating selected steps in a method forsimulating quadrature phase-shift keying (QPSK) beam forming with thesystem of the first embodiment;

FIG. 8A is a block diagram schematically representing selected elementsof a second embodiment of a system for simulating quadrature phase-shiftkeying (QPSK) beam forming in which each antenna is connected to gaincontrol unit;

FIG. 8B are a set of graphs indicating a possible set of profilesshowing an example of how the phase of the transmitted signal from eachtransmitter antenna of the second embodiment may change over time;

FIG. 8C is a flowchart indicating selected steps in a method forsimulating quadrature phase-shift keying (QPSK) beam forming with thesystem of the second embodiment;

FIG. 9A is block diagram of a system including a common binary phaseshifted shared by all antennas according to a third embodiment;

FIG. 9B are set of graphs indicating a possible set of profiles showingan example of how the phase of the transmitted signal from eachtransmitter antenna of the third embodiment may change over time.

DETAILED DESCRIPTION

Aspects of the present disclosure relate to systems and methods forsensing the surroundings of vehicles. In particular systems and methodsare described for providing vehicle mounted radar sensors operable todetect objects in the region surrounding a moving vehicle. Furthermoredirectional radar arrays are described having wide fields of view.

Vehicle mounted radar units are presented herein which are operable tosense objects surrounding vehicle to which they are mounted. The radarunit may be used to harvest information regarding the environmentthrough which it is moving. This disclosure teaches various techniquesthat a radar unit may analyze data received such that useful informationmay be gathered such as the vehicles relative speed and theidentification of hazards in its surroundings.

A radar unit with sufficient directionality may be provided by reducingside lobes. In order to reduce side lobes, signals transmitted by eachantenna of an array may be binary phase shifted according to a requiredtemporal phase shift profile. Post processing methods may be applied tothe received reflected signal over multiple time periods to simulatemultiple phase shift beam forming such as quadrature phase-shift keying(QPSK) beam forming, for example. Typically, the receivers andtransmitters may be synchronized in order to produce consistent resultsduring the time interval on which the signals are combined.

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely examples of the invention that may be embodied in various andalternative forms. The figures are not necessarily to scale; somefeatures may be exaggerated or minimized to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

In various embodiments of the disclosure, one or more tasks as describedherein may be performed by a data processor, such as a computingplatform or distributed computing system for executing a plurality ofinstructions. Optionally, the data processor includes or accesses avolatile memory for storing instructions, data or the like.Additionally, or alternatively, the data processor may access anon-volatile storage, for example, a magnetic hard-disk, flash-drive,removable media or the like, for storing instructions and/or data.

It is particularly noted that the systems and methods of the disclosureherein may not be limited in its application to the details ofconstruction and the arrangement of the components or methods set forthin the description or illustrated in the drawings and examples. Thesystems and methods of the disclosure may be capable of otherembodiments, or of being practiced and carried out in various ways andtechnologies.

Alternative methods and materials similar or equivalent to thosedescribed herein may be used in the practice or testing of embodimentsof the disclosure. Nevertheless, particular methods and materials aredescribed herein for illustrative purposes only. The materials, methods,and examples are not intended to be necessarily limiting.

Alternative methods and materials similar or equivalent to thosedescribed herein may be used in the practice or testing of embodimentsof the disclosure. Nevertheless, particular methods and materialsdescribed herein for illustrative purposes only. The materials, methods,and examples not intended to be necessarily limiting. Accordingly,various embodiments may omit, substitute, or add various procedures orcomponents as appropriate. For instance, the methods may be performed inan order different from described, and that various steps may be added,omitted or combined. In addition, aspects and components described withrespect to certain embodiments may be combined in various otherembodiments.

Reference is now made to FIG. 1A which schematically represents anexample of a vehicle mounted radar unit 100 configured to sense objectsin the region 120 surrounding a vehicle to which it is mounted. Theradar unit 100 may be mounted to various vehicles as required such asroad vehicles such cars, trucks, bikes, trailers, caravans and the like,work vehicles such as diggers, cranes, and the like as well aircraft andwatercraft where appropriate.

By way of example, the radar unit 100 may be mounted to a car and usedto detect various objects in its vicinity such as other cars 121,bicycles 122, pedestrians 123, road signs 124, walls 125, kirbs 126,trees 127 and the like.

Accordingly, the radar unit 100 may be used to harvest informationregarding the environment through which the vehicle is travelling. Thisdisclosure teaches various techniques that a radar unit may analyze datareceived such that useful information may be gathered such as thevehicles relative speed and the identification of hazards in itssurroundings.

Referring now to the block diagram of FIG. 1B selected elements arepresented of a possible radar system for sensing the surroundings of avehicle. The system includes a radar unit 110 and a controller 130. Theradar unit 110 may include a radar transmission unit 112 and a radarreceiving unit 114.

The radar transmission unit 112 includes an array of transmitterantennas TX connected to an oscillator 116 and configured to transmitelectromagnetic waves into a region surrounding the vehicle. The radarreceiving unit 114 includes at least one receiver antenna RX configuredto receive electromagnetic waves reflected by objects within the regionsurrounding the vehicle 120 and may be operable to generate raw data.

The controller 130 may include various modules such as processor units132, self-velocity calculation modules 134, wall detection modules 136,dynamic range enhancement modules 138, double reflection detectionmodules 139 and the like.

A processor unit 132 may be in communication with the radar receivingunit 114 so as to receive raw data from the radar unit 114 and generateenvironmental information based upon the received data. For example, aself-velocity calculation module 134 may be provided to calculatevelocity of the vehicle from raw data, a wall detection module 136 maybe provided to detect planar surfaces in the region surrounding thevehicle, a dynamic-range enhancement module 138 may be provided todistinguish objects reflecting weakly such as pedestrians 123 fromobjects reflecting strongly such as a wall 125 or a kirb 126 within thesame vicinity.

A double-reflection identification module 139 may be provided so as todistinguish single-reflected electromagnetic waves reflected directly byobjects towards the radar receiving unit 114 from double-reflectedelectromagnetic waves reflected indirectly from objects towards theradar receiving unit 114 via intermediate reflective surfaces. Forexample, the radar transmission unit 112 may include a circularpolarizer configured and operable to generate circularly polarizedelectromagnetic waves such as described in the applicants co-pendingU.S. Pat. Publication No. 16/802,610 which is incorporate herein in itsentirety. Accordingly, the radar receiving unit 114 may include apolarization detector configured and operable to detect the polarizationof the received electromagnetic waves.

Circular polarized electromagnetic waves reverse their polarity uponreflection such that waves reflecting an even number of times may bereadily distinguished from waves reflecting an odd number of times. Ifthe polarization of the received waves matches the polarization of thetransmitted waves then they may be considered to have been receiveddirectly from a reflecting object. If the polarization of the receivedwaves is reversed, the waves may be considered to have been receivedindirectly via secondary reflectors.

Reference is now made to the flowchart of FIG. 2A which indicatesselected steps in a possible method for sensing the surroundings of avehicle 200. The method may include any or all of the following stepsproviding a vehicle mounted radar unit comprising a radar transmissionunit comprising an array of transmitter antennas connected to anoscillator, and a radar receiving unit comprising at least one receiverantenna, and a processor unit in communication with the radar receivingunit 210; transmitting electromagnetic radiation into the regionsurrounding the vehicle 220; receiving electromagnetic radiationreflected from an object in the region surrounding the vehicle 230;detecting polarization of received electromagnetic waves 240; detectingtwo dimensional extended targets within the region surrounding thevehicle 250; distinguishing objects reflecting weakly from objectsreflecting strongly within the same vicinity possibly by applyingdynamic-range enhancement filter combinations 260; constructing a seriesof three dimensional images of the region surrounding the vehicle 270;and analyzing the series of three dimensional images to determine thevelocity of the vehicle 280.

It is noted that the above described steps of the method for sensing thesurroundings of a vehicle 200 may be carried out in various combinationsand various orders as suit requirements. Where necessary, those skilledin the art may include still further steps.

FIGS. 2B and 2C present the substeps of possible methods for carryingout the steps of the steps of constructing a series of three dimensionalimages 280 and detecting two dimensional extended targets in the regionsurrounding a vehicle 250.

Referring now to the flowchart of FIG. 2B the substeps of a possiblemethod are detailed for carrying out the step of constructing a seriesof three dimensional images 280. The substeps include constructing atleast a first three dimensional image representing the regionsurrounding the vehicle at a first instant 281; waiting for a delaytime, dt and constructing a second three dimensional image representingthe region surrounding the vehicle at a second instant 282; detectingcommon reflecting objects in the first three dimensional image and thesecond three dimensional image 283; determining a horizontal shift, dx,for detected common reflecting objects 284; and calculating a gradientof a trendline through a plot of apparent radial velocity v_(R) as afunction of horizontal shift dx for the reflecting objects 285.

Accordingly the self-velocity calculation module may include an imagegeneration unit, and a memory unit. The image generation unit isconfigured and operable to construct three dimensional imagesrepresenting the region surrounding the vehicle, and the memory unit isconfigured and operable to store data pertaining to a series includingat least a first three dimensional image representing the regionsurrounding the vehicle at a first instant, and a second threedimensional image representing the region surrounding the vehicle at asecond instant after a delay time, dt.

So as to better illustrate the method of self-velocity determinationreference is now made to FIGS. 3A-D which schematically represent aradar unit of the disclosure 300 mounted to a moving vehicle 310detecting apparent movement of objects 322, 324 in the regionsurrounding the vehicle 310.

As illustrated in FIG. 3A and FIG. 3B showing a side view and a top viewof a vehicle, the position 320 of a reflecting object may be defined byat least a horizontal spatial coordinate, x, a vertical spatialcoordinate, y, and a radial spatial coordinate, R.

Accordingly, a three dimensional image may constructed of the regionsurrounding the vehicle by constructing a matrix of voxels, each voxelcharacterized by a set of voxel parameters including: a horizontalspatial coordinate, x, of a reflecting object along an axis parallel tothe path of the vehicle; a vertical spatial coordinate, y, of thereflecting object along a vertical axis orthogonal to the path of thevehicle; a radial spatial coordinate, R, of the reflecting object alongan axis diverging radially from the vehicle. Each voxel may further beassociated with an intensity value indicating the energy of radiationreflected therefrom, and a Doppler-shift value which may indicate theapparent radial velocity v_(R) of any reflecting object located at thosecoordinates in the region around the vehicle. It is noted that evenstationary objects will typically have an apparent radial velocity whendetected by a sensor mounted to moving vehicle.

The corresponding three dimensional images may include clusters orshapes of high intensity voxels which are characteristic of reflectingobjects in the region surrounding the vehicle. Accordingly, anx-coordinate, x_(n), and a y-coordinate, y_(n), may be determined foreach reflecting object in each three dimensional image.

As a series of such three dimensional is generated, and each threedimensional image is stored in a local memory unit, common reflectingobjects may be identified at different coordinates in two or more threedimensional images. Accordingly a horizontal shift dx between a pair ofthree dimensional images may be defined by finding the reflectingobject’s co-altitude angle, θ_(n), by calculating the arctangent of theratio (x_(n)/y_(n)) of the x-coordinate of the reflecting object and they-coordinate of the reflecting object an angle; and calculating the sineof the co-altitude angle such that dx=sin(arctan(x_(n)/y_(n)). Thus thehorizontal shift is defined as dx

$\overset{\text{def}}{=}$

sin atan

$\left( \frac{x}{y} \right)$

As illustrated in FIGS. 3C and 3D a stationary reflecting objectsituated at a point 321 relatively close to the radar unit 300 willtypically have a large horizontal shift dx₁ whereas a stationaryreflecting object situated at a point 322 relatively further from theradar unit 300 will typically have a larger horizontal shift dx₂. It isfurther noted that each reflecting object is further characterized byits apparent radial speed v_(R1), v_(R2).

It can be shown that for each stationary reflecting object the apparentradial speed relates to the horizontal shift according to the functionv_(R) = v_(car) · dx. Accordingly, when a graph is plotted representingthe radial speed values of all detected objects against theircorresponding horizontal shifts, a trend line may be constructed, forexample using the method of least squares and the gradient of theresulting trendline may indicate the velocity of the vehicle v_(car).

By way of illustration, FIGS. 4A-C are three examples of such plots ofapparent radial velocity v_(R) as a function of horizontal shift dx forthe reflecting objects as measured by radar units mounted to vehiclestravelling at different speeds. FIG. 4A represents the plot of radialspeed against horizontal shift as recorded by a stationary vehicle. Thegradient of the resulting line is flat indicating no movement of thevehicle.

FIG. 4B represents the plot of radial speed against horizontal shift asrecorded by a vehicle travelling at 20kph and FIG. 4C represents theplot of radial speed against horizontal shift as recorded by a vehicletravelling at 40kph. It is noted that as the speed of the vehiclev_(car) increases, so the gradient of the trend line increases inproportion.

Referring back now to the flowchart of FIG. 2C the substeps of apossible method are detailed for carrying out the step of detecting twodimensional extended targets in the region surrounding a vehicle 250.The substeps include detecting a spectral-reflection point in reflectedradiation 251; constructing virtual box around volume containing acandidate wall-object 252; calculating energy-profile for the radarimage within the virtual box 253; and applying a classification functionto the energy-profile 254. By way of example, the classificationfunction may involve calculating at least one wall-indication parameterselected from a group consisting of: overall energy reflected fromwithin virtual box; profile of reflected energy from within virtual boxsegments; number of voxels within virtual box having energy values abovea threshold value; and combinations thereof.

It is noted that whilst it is of importance for vehicle to be abledetect prolonged objects such as walls and the like within theirsurroundings, radar-based far-field sensors may encounter a problem whenrepresenting the dimensions of such extended or complex shapes.

By way of example, signals reflected from an extended wall may consistof a dominant reflection from a single specular point, and much weakerdiffraction and “diffusive” reflections which may be harder to detect.Nevertheless, the ability to estimate the dimensions of the detectedobjects can be crucial for various radar-applications, and especially inautomotive-radars applications -where the edges of an elongated obstaclemay pertain to the determination and maintenance of a safe drivingroute.

Accordingly, systems of the system described herein may include a walldetection module operable to detect planar surfaces in the region of thevehicle by applying a method for detecting and classifying elongatedtwo-dimensional obstacles such as walls, fences, curbs and the like. Themodule may further be operable to differentiate such obstacles fromsingle localized objects such as pedestrians, poles, road-signs and thelike. In particular, the wall detection module may include a processingunit, and a memory unit storing executable code directed towardscomparing energy-profile within a virtual box with a referenceenergy-profile indicative of a two dimensional reflector.

Methods may include the detection of the strongest reflection from anobject and estimation of the object’s dimensions from the radar-imageenergy profile along the object. The strongest reflection will bedetected from the object’s specular-reflection point.

Referring now to FIG. 5 a radar unit 500 of the disclosure mounted to amoving vehicle 510 may detect a wall-type two dimensional extendedtarget 520 in the region surrounding the vehicle by identifying aspecular-point 530. It is particularly noted that for two dimensionalobjects, the specular-reflection point is typically tangential to thespecular-point 530 and perpendicular to the normal between the sensorand the specular point. For millimeter wave range radars, multiple weakreflections are expected from along the extended surface of the twodimensional object. Accordingly, a virtual box 540 may be constructed tocontain the expected volume of the wall and the energy-profile of theradar-image within the virtual box may be calculated.

Having calculated an energy-profile for the radar-image within thevirtual box, a classification function may be applied to determinelikelihood of the object being a wall-object. For example, theclassification function may calculate and combine variouswall-indication parameters such as: overall energy integrated for allreflections within the volume contained with the virtual box volume,energy integrated for all reflections within segments within the virtualbox, the number of voxels within the box which pass certainthreshold-value, or the use of voxel clustering within the box such asK-means, DBSCAN or the like. Various classification-methods can beapplied on the extracted features, such as hard-threshold, SVM, NN \ CNNetc.

It is noted that the dimensions of the candidate wall-object may beevaluated by a variety of methods such as, the following examples. Aroot mean square value may be calculated for the energy distributionwithin the box, possibly excluding the specular-reflection itself.Additionally or alternatively the continuity of voxels passing a certainthreshold value may be determined. Still further, the dimensions of amain cluster may be determined after applying clustering algorithm onthe voxels within the box.

Where appropriate, for example where a wide field of view is providedalong a horizontal axis, the velocity-profile of reflections along anelongated target may be determined using self-velocity determinationtechniques such as described herein. Accordingly, it may be possible toincrease the reliability of wall-object detection by referring to thehistory and the relative velocity of the specular reflection withrespect to the sensor. For example, a constant zero relative velocity ofa strong reflection detected by a moving sensor might indicate thepresence of an elongated object parallel to the motion of the vehicle.

It is further noted that different objects may reflect electromagneticradiation at different intensities. Thus there is a danger of moreweakly reflecting objects may become obscured by more dominantreflections from objects reflecting strongly in the same vicinity. Forexample, parked vehicles may reflect more strongly than pedestrians,plastic piping may reflect more weakly than a structural-wall from whichit is protrudes, in such cases the weaker reflection may be difficult todistinguish from the stronger reflection.

Accordingly, systems described herein may include a dynamic rangeenhancement module configured and operable to distinguish objectsreflecting weakly from objects reflecting strongly within the samevicinity.

One method of enhancing weak targets may be by applying a dedicatedfilter to match the expected properties of a certain target. However,this may come at the expense of other targets of interest, possiblyattenuating and degrading their detectability.

It has surprisingly been found that the dynamic-range may be enhanced bycombining several filters over the same image. For example an unfilteredimage may be merged with a filtered image to enhance weak reflections.

According to one possible combination, a finite impulse response (FIR)filtering or infinite impulse response (IIR) filtering may be mergedwith a radar-image without temporal-filter over multiple frames. Such acombination may be useful for enhancing weak but dynamic objects. Suchdynamic objects include pedestrians, bicycles or other vehicles whosemovement may be inherent. Other dynamic objects may be stationaryobjects whose apparent movement is induced by the moving vehicle-mounteddetector, for example a thin and localized object such as a plastic pipeagainst an extended surface such as a semi-static wall which may appearto be stationary relative to the vehicle.

According to another possible enhancement technique, various high-passfilters or band-pass filters may be applied over multiple frames suchthat several images are generated, each one expected to correspond to adifferent time scale.

Still another enhancement technique may include Doppler-domainfiltering. Where Doppler-resolution is possible, the expected Dopplerhistogram associated with the movement of large-static objects may beremoved over their predicted volumes. This may leave a micro-Dopplersignature of the weaker but more dynamic targets (e.g. pedestrians).

Accordingly, a multi-layer image may be introduced comprising multiplelayers each layer corresponding to a different filter. Thus the layersmay combined in various combinations. It is further noted that whererequired feature extraction may be performed for each layer separatelysuch as by generating a point-cloud image and detecting features thereinsuch as described in the applicants copending U.S. Provisional Pat.Application No. 62/955482 which is incorporated herein by reference inits entirety. Additionally or alternatively, where preferred, a commonfeature extraction procedure may be performed upon multiple layerssimultaneously. Similarly, data from one layer may be used to supportdata-processing from other layers as required, for example fortarget-detection reinforcement.

Reference is now made to FIG. 6A and FIG. 6B. FIG. 1A shows how asteering vector may be generated by BPSK phase shifting. With noartificial phase shifting, an array of antennas may produce a range ofphase shifts due to the nature of the electronic circuits and the like,plus the phases generated by wave propagation to a desired steeringdirection (termed “array factor”). This range of phases is representedin the circular range of FIG. 6A(i). The phasors shown in the figure donot add up coherently. By selectively adding a 180 degree phase shift toall the antennas producing phases within the left side of the circle, itis possible to partially align these phasors as shown in FIG. 6A(ii),and thus emit energy toward the desired steering direction. Accordingly,each antenna 1116 of the array may be connected to the signal generatingoscillator 1112 via a binary phase shifter 1114, as shown in FIG. 6B.Although the BPSK mechanism may indeed generate a steering vector 1110,the resultant beam suffers significant side lobes and large losses.

A more efficient steering vector may be generated by providing furtherphase shift options. Referring to FIGS. 6C and 6D, a range of phasessuch as shown in FIG. 6C(iii) may be converted into a net steeringvector 1130 such as shown in FIG. 1C(iv) by selectively shifting eachtransmitted signal by 0, 90, 180 or 270 degrees as required (QPSK).

FIG. 6D illustrates a possible hardware arrangement 1140 for producingsuch phase shifts in an antenna 1148 of the array. Each antenna 1148 ofthe array may be connected to the signal generating oscillator 1142 viaa phase shifting mechanism having two parallel arms an in-phase arm(Re), and a quadrature arm (Im).

The in-phase arm (Re) includes a first binary phase shifter 1144 whichmay be selectively activated to add a 180 degree phase shift to theoscillating signal as required. Alternatively, by not activating thefirst binary phase shifter the signal is transferred to the transmittingantenna in phase.

The quadrature arm (lm) includes a second binary phase shifter 1146 anda quarter cycle phase shifter 1145. The quarter cycle phase shifter 1145is configured to add a 90 degree phase shift to the oscillating signal.Accordingly, if the second binary phase shifter 1146 is not activated a90 degree phase shift is applied to the signal transferred to theantenna. Alternatively, if the second binary phase shifter is activatedto add a further 180 degree phase shift, a total phase shift of 270degree is applied to the signal transferred to the antenna as required.

It will be appreciated that such a hardware quadrature modulationmechanism such as shown in FIG. 6D may significantly improve the overallsteering vector. However, the arrangement requires significantly morehardware elements than the simple binary phase shifter 1120 of FIG. 6B.The addition of a quadrature arm for each antenna, including a quartercycle phase shifter which may need to be located physically close to theantenna itself, places significant hardware constraints on thearchitects of antenna array circuits.

A possible solution for generating improved steering vectors using onlythe binary phase shifter elements is described here.

Referring now to the block diagram of FIG. 7A, selected elements arerepresented of a first embodiment of a system for simulating quadraturephase-shift keying (QPSK) beam forming in an antenna array 1200. Thesystem includes a transmitter 1250, an antenna array 1210, a binaryphase shifter 1220 associated with each transmitting antenna, acontroller 1230, a receiving antenna 1240; and a post processor 1260.

The transmitter 1250 is configured and operable to generate anoscillating signal for transmission by the antenna array 1210. It isnoted, that where appropriate, the transmitter 1250 may be furtheroperable to generate a signal sweeping through a range of frequencies,or a chirp.

The antenna array 1210 includes a number of antennas A1-n. Each antennais operable to transmit the signal generated by the oscillator 1270simultaneously with a required phase shift. It will be noted that thesuperposition of the transmitted signals from all the antennas in thearray produces an overall signal beam having a characteristic shape.

The binary phase shifter 1220 associated with each transmitting antennaAn is configured and operable to selectively apply a phase shift of 180degrees to the oscillating signal as required. Alternatively, if thebinary phase shifter 1220 is not activated, no phase shift is applied tothe oscillating signal. Accordingly, the signal transmitted by theassociated antenna is either in phase or in anti-phase with theoscillating signal produced by the oscillator 1270, as required.

The controller 1230 is configured to send activation instructions to thebinary phase shifters 1220 such that only the required antennas transmitphase shifted signals.

The (one or more) receiving antenna 1240 is configured to receive returnsignals reflected from targets.

The post processor 1260 is operable to manipulate received signals andincludes a memory 1280 element and a processing unit 1290. The memoryelement 1280 is operable to save received signals. The processing unitis operable to apply phase shifts to selected received signals stored inthe memory 1280, and further operable to sum received signals stored inthe memory 1280.

In particular examples, the processing unit may apply a 90 degree phaseshift to selected received signals and to sum these with other receivedsignals to produce a required output signal.

Accordingly, the controller may be operable to determine a requiredcomplex steering vector C = R + jl for each antenna of the array. Thecomplex steering vector C includes a binary real component R selectedfrom +1 and -1 and a binary imaginary component I selected from +1 and-1. The value of +1 indicates that no phase shift is required and thecomponent of -1 indicates that a phase shift is required. Thus the realcomponent may represent a required phase shift selected from 0 and 180degrees and an imaginary the component may represent a required phaseshift selected from 90 and 270 degrees, all with reference to theR=+1,1=+1 combination.

Referring now to the graphs of FIG. 7B which indicate a possible set ofprofiles showing an example of how the phase of the transmitted signalS1-n from each transmitter antenna A1-n of the first embodiment maychange over time.

It is noted that the phase shift of each antenna remains fixed for agiven time interval Δt. Each antenna An receives a unique profiledetermined by the required steering vector Ci at that time. Each complexsteering vector Ci may determine the required phase shifts for twoconsecutive time intervals Δti, Δti+1.

During a first time interval Δti, the controller instructs binary phaseshifters 1220 of antennas A1-n having an associated steering vector Ciwith a real component Ri of -1 to apply a 180 degree phase shift to thetransmitted signal.

During a second time interval Δti+1, the controller instructs binaryphase shifters 1220 of antennas having an associated steering vector Ciwith an imaginary I component of -1 to apply a 180 degree phase shift tothe transmitted signal.

Accordingly, the post processor 1260 may be operable to store reflectedsignals received during the first time interval and the second timeinterval in the memory. The processor unit may then apply a 90 degreephase shift to signals received during the second time interval beforesumming the signals received during the first time interval to 90 degreephase shifted signals received during the second time interval.

The resulting output signal from the post processor will have thecharacteristics of a quadrature phase shifted signal.

Referring now to the flowchart of FIG. 7C, selected steps are indicatedof a method 1400 for simulating quadrature phase-shift keying (QPSK)beam forming with the system of FIG. 7A in which the antennas of thearray 1210 are each connected to a common transmitter via a binary phaseshifter 1220.

For each transmitting antenna of the array a required complex QPSKsteering vector C is determined 1410 comprising a real component Rselected from +1 and -1 and a binary imaginary component I selected from+1 and -1.

The transmitter generates an oscillating signal 1420 which is passed toeach antenna via the binary phase shifter. Optionally, each transmittedsignal may sweep over a range of frequencies during each time interval.

During a first time interval 1430, for each transmitting antenna havingan associated steering vector with a real component R of +1, theassociated binary phase shifter applies a 180 degree phase shift to thetransmitted signal 1432, the antenna transmits the signal 1434 and thereceived signal is stored in the memory of the postprocessor 1436.

During a second time interval 1440, for each transmitting antenna havingan associated steering vector with an imaginary component I of +1, theassociated binary phase shifter applies a 180 degree phase shift to thetransmitted signal 1442, the antenna transmits the signal 1444 and thereceived signal is stored in the memory of the postprocessor 1446.

The post processor may then apply a 90 degree phase shift to signalsreceived 1450 during the second time interval 1440 and sum the signalsreceived during the first time interval to 90 degree phase shiftedsignals received during the second time interval 1460.

A particular feature of the systems and methods described herein is thelinear combination of the received signal over several time intervals inorder to simulate and benefit from the advantages of an enhancedbeamformer in a simulated manner. This feature can be extended invarious forms which will be clear to those skilled in the art and arementioned here as examples.

In one extension where the transmitter already supports beamformingusing a certain choice of phases (e.g. 4 phases QPSK, 8 phases 8-PSK,etc.), or gains, the combination of M codewords (two or more) over Mtime intervals can be used in order to generate a larger choice ofphases by factor M (as for example, using 4 time intervals with BPSK or2 time intervals with QPSK to generate simulated 8-PSK).

The simulated QPSK scheme can be alternatively described by taking adesired phasor C per transmit antenna, transmitting

X = Sgn(Re{C ⋅ e^(−jϕ)})

, where Φ is 0 for the first interval and 90 degrees for the secondinterval, and then compensating for this phase in the received bymultiplying with e^(jΦ). In another extension of the current invention,the sequence of the “modulating” phase Φ can be chosen in different waysover time, for example in different scanned frequencies or frames.

In another extension of the invention, the received signals over the Mintervals are combined with arbitrary phasors a₁, .. a_(M) notnecessarily having unit gain (instead of a₁ = 1,a₂ = j for the case ofQPSK as described herein). The beamforming codewords over these Mintervals are chosen in a way that their linear combination weighted bya₁,..a_(M) yields desired characteristics (such as a high peak tosidelobe level).

The method described above for implementing QPSK (4 phases) beamformingby using binary phase shifters and two time-intervals is presented forillustrative purposes only. This method may be further generalized toimplement any even number 2n of phases over n time-intervals. Forexample, with three time-intervals, a 6-PSK modulation may be achieved.

For N time intervals, a method may be implemented in which a transmitterapplies a 180 degree phase shift selectively to particular antennasaccording to the following conditions. In the n-th time interval, a 180degree phase shift is applied to the k-th antenna if the real value ofthe steering vector rotated by -n*180/N degrees is negative. Thus, forthe k-th antenna a 180 degree phase shift is applied if the followingformula is true:

Real(C_(k) * e^(−j*φ[n])) < 0,

where C_(k) is the k-th component of the steering vector, and φ_(n) =πn/N is the rotation sequence.

Accordingly, where appropriate, in the post-processor, a rotation of φnradians maybe applied for the n-th time-interval, before summation ofthe received signal in all time intervals.

A method such as described herein may be extended to incorporate furthercriteria for the desired beamformer, by choosing a set of N phase shiftsequences such that the mean of the transmitted signal over the N timeintervals satisfies the desired criteria. For example, effectiveattenuation for a specific transmitter antenna may be required for gaincontrol for apodization and transmitter gain equalization. This may beachieved, even without analog gain control, by using a specific rotationsequence for a specific transmit antenna, for example the steeringvector for each antenna may be rotated by an angular step (1-a)*φn, say,where the value of a is selected specifically to suit each transmitterantenna).

The multiple time-intervals, needed for applying the described method,may further be used for other purposes. In one possible embodiment,multiple time-intervals may be used to allow Doppler processing withineach Frame, in order to allow for an integration time that may be longerthan the channel coherence time as well as for obtaining informationregarding the velocity of targets. Each spatial transmitter direction tobe scanned may include N time-intervals, and the Doppler post-processingmay search for a linear phase shift between intervals that maycorrespond to a radial velocity. This may be implemented, for exampleusing a Fast Fourier Transformation (FFT) over the time-intervals.

It is noted that, where appropriate, each time-interval may itselfinclude sweeping the transmitted signal over multiple frequencies usinga stepped frequency continuous wave, a Chirp or some other frequencyfunction over time for the duration of the time-interval. Accordingly,by changing the beamformer between time-intervals as described abovesidelobe levels would typically be reduced due to phase quantization atany given velocity. Nevertheless, the associated beamformingquantization errors may generate sidelobes at other velocities.

It is another feature of the current method that the spectral shape ofthe sidelobes which are generated may be controlled by selecting aspecific order for the time-intervals, such that most of thequantization noise which generates the sidelobes is limited to highfrequencies, which correspond to radial velocities higher than thoseexpected in the specific application. Where required, the phase rotationφn for the n-th time-interval (where n may take any integer value from 0to N-1), may be selected such that:

φ_(n) = Π * [(n*(N-1)/2)mod N],

where the “mod” is the modulo operation which returns the remainder ofdivision by a given integer and it is assumed that N is an integermultiple of 4. As above, the 180 degrees rotation may be applied in thetransmitter only if Real(Ck*e-j*φ[n])<0, and the post-processor appliesa rotation by φn. With such a reordering of the time-intervals, most ofthe sidelobes power resides at the Nyquist frequency of the Doppler.

It will be appreciated that other constructions may be used forselecting the order in the phase rotation sequence, or the sequence ofsteering vectors, so as to optimize the spectral shape of thequantization noise, as suit requirements.

In the construction above, a known required steering vector is rotatedby φ_(n) for the binary phase selection. An alternative approach, forexample where the required steering vector is not known, may involvesearching for the phase selection at the transmitter for which the valueof Real(H({b_(k)})*exp(j*φ_(n))) is maximal, where H({b_(k)}) is thephasor representing the combination of all transmitting antennas in thedesired spatial direction with a specific phase selection b_(k). Suchmaximization can be performed in various ways for example by exhaustivesearch over all binary phase combinations (with K transmit antennasthere are 2^(K) options). H may be obtained, for example, by analysis ofdirect measurements of electromagnetic waves reflected by a referencetarget located in a desired spatial direction.

The number of time-intervals may be selected so as to achieve therequired beamforming accuracy in terms of, for example, sidelobes level,signal to noise ratio (SNR) (possibly using a longer integration time byadding intervals) and Doppler estimation resolution. On the other hand,the number of time intervals may be limited by other factors such asmemory capacity and processing power of the electronic components, andavoidance of blur in the Frame. Accordingly, the actual number oftime-intervals selected may be a compromise of all these considerations.

As some spatial directions might be more important than others, in termsof the needed SNR and Doppler resolution, it may be preferred that moretime-intervals are allocated to those preferred directions, and fewer toother lower priority directions.

This scanning scheme may be used in various applications such as anexterior car radar sensor, used for ADAS (Advanced Driver AssistanceSystem) or autonomous driving. In such an application, it will beappreciated that the horizontal angular range of interest (azimuthrange) is typically wider than the vertical angular range of interest,(elevation range). This is because the car radar sensor is not generallyrequired to scan beneath the road surface. Accordingly, it may bepreferred to align the transmitter antennas in a vertical linear arraysuch that the side lobes lie outside the high priority elevation range.The receiver antennas may be arranged in an orthogonally orientatedhorizontal linear array.

Other possible applications may include the monitoring of an enclosedspace such as a room, a playing field, a goal-line or the like. Stillother applications may involve the tracking of objects within a targetregion, possibly using large-arrays for body-scanning. Still otherapplications will occur to those skilled in the art.

Referring now to the block diagram of FIG. 8A, which schematicallyrepresents selected elements of a second embodiment of a system in whicheach antenna is connected to gain control unit 1550 such that quadratureamplitude modulation (QAM) beam forming may be simulated.

In addition to the components shown in the first embodiment system ofFIG. 7A, a dedicated gain control unit 1530 is associated with eachtransmitting antenna. Accordingly, the controller is further configuredto instructions to the gain control units to amplify the transmittedsignal by a required gain determined by the complex steering vector.

The controller may again be operable to determine a required complexsteering vector C = R +jl for each antenna of the array. Here, however,the steering vectors may have a continuous real component R selectedfrom the range +1 > R > -1 and a continuous imaginary component Iselected from the range +1 > I > -1.

Accordingly, the controller may be further operable to select a requiredamplitude R for the real component of the associated steering vector andduring the first time interval instruct the associated gain control unitto apply an associated first gain GR to the transmitted signal.Similarly the controller is operable to select a required amplitude Ifor the imaginary component of the associated steering vector and duringthe second time interval instruct the associated gain control unit toapply a second gain GI to the transmitted signal wherein the second gainGI is equal to the product of GR and the absolute ratio of I to R.

Referring to the set of graphs shown in FIG. 8B, the resulting signalsproduced by each antenna during each time period may thus be amplitudemodulated as well as phase modulated.

Referring now to the flowchart of FIG. 8C, selected steps are indicatedof a method for simulating quadrature amplitude modulation (QAM) beamforming with the system of FIG. 8A in which the antennas of the arrayare each connected to a common transmitter via an associated binaryphase shifter and a gain control unit 1530.

For each transmitting antenna of the array a required complex QPSKsteering vector C is determined 1610 comprising a real component Rselected from the range +1 > R > -1 and an imaginary component Iselected from the range +1 > I > -1.

The transmitter generates an oscillating signal 1620 which is passed toeach antenna via the binary phase shifter. Optionally, each transmittedsignal may sweep over a range of frequencies during each time interval.

During a first time interval 1630, for each transmitting antenna havingan associated steering vector with a negative real component R, theassociated binary phase shifter applies a 180 degree phase shift to thetransmitted signal 1632. The associated gain control unit amplifies thesignal by a first value GR=|R|G0 1633, the antenna transmits theamplified signal 1634 and the received signal is stored in the memory ofthe postprocessor 1636.

During a second time interval 1640, for each transmitting antenna havingan associated steering vector with a negative imaginary component I, theassociated binary phase shifter applies a 180 degree phase shift to thetransmitted signal 1642. The associated gain control unit amplifies thesignal by a second value GI = |I|G0 1643 Then the antenna transmits theamplified signal 1644 and the received signal is again stored in thememory of the post-processor 1646.

Accordingly, when the post processor may applies a 90 degree phase shift1650 to signals received during the second time 1640 interval and sumsthese signals 1660 with the signals received during the first timeinterval, the resultant signal may have a virtual phase shift of anyvalue required.

It is further noted that although systems described herein include adedicated binary phase shifter for each antenna, alternative systems mayoperate without phase shifters, by utilizing additional time intervals,as illustrated in FIG. 9A.

Using such a system may be enabled by activating only those antennashaving a real component of +1 for a first time period without a phaseshift, activating only those antennas having a real component of -1 fora second time period where a phase shift of 180 degrees is applied atthe receiver, activating only those antennas having an imaginarycomponent of +1 for a third time period without a phase shift,activating only those antennas having an imaginary component of -1 for afourth time period and applying a phase shift of 180 degrees at thereceiver.

It is further noted that provided that each antenna of a system has anindependently controllable connecting switch 1740, such as illustratedin FIG. 9A, it may be possible to apply such phase shifts directly fromthe oscillator 1770 or during post processing. Additionally oralternatively, a common binary phase shifter may be connected tomultiple transmitting antennas as required.

An example of the signal profiles produced by an example of such asystem are presented in FIG. 4B. The post processor may store receivedsignals from each of the first time period, the second time period, thethird time period and the fourth time period in the memory.

The four signals may be summed by the receiver after applying a 0, 180,90, 270 degree phase shift to the first, second, third and fourth step,respectively. By summing all these signals a simulated QPSK steeringvector may be achieved in a system without phase shifters.

Still further extensions of the linear combination of a received signalover multiple time intervals will occur to those skilled in the art.

Technical Notes

Technical and scientific terms used herein should have the same meaningas commonly understood by one of ordinary skill in the art to which thedisclosure pertains. Nevertheless, it is expected that during the lifeof a patent maturing from this application many relevant systems andmethods will be developed. Accordingly, the scope of the terms such ascomputing unit, network, display, memory, server and the like areintended to include all such new technologies a priori.

As used herein the term “about” refers to at least ± 10 %.

The terms “comprises”, “comprising”, “includes”, “including”, “having”and their conjugates mean “including but not limited to” and indicatethat the components listed are included, but not generally to theexclusion of other components. Such terms encompass the terms“consisting of” and “consisting essentially of”.

The phrase “consisting essentially of” means that the composition ormethod may include additional ingredients and/or steps, but only if theadditional ingredients and/or steps do not materially alter the basicand novel characteristics of the claimed composition or method.

As used herein, the singular form “a”, “an” and “the” may include pluralreferences unless the context clearly dictates otherwise. For example,the term “a compound” or “at least one compound” may include a pluralityof compounds, including mixtures thereof.

The word “exemplary” is used herein to mean “serving as an example,instance or illustration”. Any embodiment described as “exemplary” isnot necessarily to be construed as preferred or advantageous over otherembodiments or to exclude the incorporation of features from otherembodiments.

The word “optionally” is used herein to mean “is provided in someembodiments and not provided in other embodiments”. Any particularembodiment of the disclosure may include a plurality of “optional”features unless such features conflict.

Whenever a numerical range is indicated herein, it is meant to includeany cited numeral (fractional or integral) within the indicated range.The phrases “ranging/ranges between” a first indicate number and asecond indicate number and “ranging/ranges from” a first indicate number“to” a second indicate number are used herein interchangeably and aremeant to include the first and second indicated numbers and all thefractional and integral numerals therebetween. It should be understood,therefore, that the description in range format is merely forconvenience and brevity and should not be construed as an inflexiblelimitation on the scope of the disclosure. Accordingly, the descriptionof a range should be considered to have specifically disclosed all thepossible sub-ranges as well as individual numerical values within thatrange. For example, description of a range such as from 1 to 6 should beconsidered to have specifically disclosed sub-ranges such as from 1 to3, from 1 to 4, from 1 to 5, from 7 to 4, from 7 to 6, from 3 to 6 etc.,as well as individual numbers within that range, for example, 1, 7, 3,4, 5, and 6 as well as non-integral intermediate values. This appliesregardless of the breadth of the range.

It is appreciated that certain features of the disclosure, which are,for clarity, described in the context of separate embodiments, may alsobe provided in combination in a single embodiment. Conversely, variousfeatures of the disclosure, which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable sub-combination or as suitable in any other describedembodiment of the disclosure. Certain features described in the contextof various embodiments are not to be considered essential features ofthose embodiments unless the embodiment is inoperative without thoseelements.

Although the disclosure has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims.

All publications, patents and patent applications mentioned in thisspecification are herein incorporated in their entirety by referenceinto the specification, to the same extent as if each individualpublication, patent or patent application was specifically andindividually indicated to be incorporated herein by reference. Inaddition, citation or identification of any reference in thisapplication shall not be construed as an admission that such referenceis available as prior art to the present disclosure. To the extent thatsection headings are used, they should not be construed as necessarilylimiting.

The scope of the disclosed subject matter is defined by the appendedclaims and includes both combinations and sub combinations of thevarious features described hereinabove as well as variations andmodifications thereof, which would occur to persons skilled in the artupon reading the foregoing description.

What is claimed is:
 1. A system for sensing the surroundings of a vehicle comprising: a vehicle mounted radar unit comprising: a radar transmission unit comprising an array of transmitter antennas connected to an oscillator and configured to transmit electromagnetic waves into a region surrounding the vehicle, and a radar receiving unit comprising at least one receiver antenna configured to receive electromagnetic waves reflected by objects within the region surrounding the vehicle and operable to generate raw data; a processor unit in communication with the radar receiving unit and configured to receive raw data from the radar unit and operable to generate environmental information based upon the received data; wherein the processor comprises a self velocity calculation module operable to calculate velocity of the vehicle from raw data; and wherein the self-velocity calculation module is operable to determine a horizontal shift, dx, for detected reflecting objects; and to calculate a gradient of a plot of apparent radial velocity V_(R) as a function of horizontal shift dx for the reflecting objects.
 2. The system of claim 1 wherein the self-velocity calculation module comprises an image generation unit and a memory unit.
 3. The system of claim 2 wherein the image generation unit is configured and operable to construct a three dimensional image representing a region surrounding the vehicle comprising a matrix of voxels.
 4. The system of claim 3 wherein each voxel characterized by a set of voxel parameters including: a horizontal spatial coordinate, x, of a reflecting object along an axis parallel to the path of the vehicle; a vertical spatial coordinate, y, of the reflecting object along a vertical axis orthogonal to the path of the vehicle; a radial spatial coordinate, R, of the reflecting object along an axis diverging radially from the vehicle; an intensity value; and a Doppler-shift value indicating an apparent radial velocity V_(R) of the reflecting object.
 5. The system of claim 2 wherein the memory unit configured to store data pertaining to at least: a first three dimensional image representing the region surrounding the vehicle at a first instant, and a second three dimensional image representing the region surrounding the vehicle at a second instant after a delay time, dt.
 6. The system of claim 1 wherein the processor is operable to determine horizontal shift, dx, by: determining an x-coordinate, xn, for the reflecting object; determining a y-coordinate, yn, for the reflecting object; finding the reflecting object’s co-altitude angle, θn, by calculating the arctangent of the ratio (xn/yn) of the x-coordinate of the reflecting object and the y-coordinate of the reflecting object an angle; calculating the sine of the co-altitude angel such that dx=sin(arctan(xn/yn)).
 7. The system of claim 1 wherein the processor further comprises a wall detection module operable to detect planar surfaces in the region surrounding the vehicle.
 8. The system of claim 7 wherein the wall detection module comprises a processing unit, and a memory unit storing executable code directed towards comparing energy-profile within a virtual box with a reference energy-profile indicative of a two dimensional reflector.
 9. The system of claim 1 wherein the radar transmission unit further comprises a polarizer configured and operable to generate circularly polarized electromagnetic waves.
 10. The system of claim 1 wherein the radar receiving unit further comprises a polarization detector configured and operable to detect the polarization of the received electromagnetic waves.
 11. The system of claim 1 further comprising a double-reflection identification module comprising: a circular polarizer configured and operable to generate circularly polarized electromagnetic waves; and a polarization detector configured and operable to detect the polarization of the received electromagnetic waves.
 12. A system for sensing the surroundings of a vehicle comprising: a vehicle mounted radar unit comprising: a radar transmission unit comprising an array of transmitter antennas connected to an oscillator and configured to transmit electromagnetic waves into a region surrounding the vehicle, and a radar receiving unit comprising at least one receiver antenna configured to receive electromagnetic waves reflected by objects within the region surrounding the vehicle and operable to generate raw data; a processor unit in communication with the radar receiving unit and configured to receive raw data from the radar unit and operable to generate environmental information based upon the received data; wherein the processor comprises a wall detection module operable to detect planar surfaces in the region surrounding the vehicle.
 13. The system of claim 12 wherein the wall detection module comprises a processing unit, and a memory unit storing executable code directed towards comparing energy-profile within a virtual box with a reference energy-profile indicative of a two dimensional reflector.
 14. The system of claim 12 wherein the wall detection module is configured and operable to detect a two dimensional extended target in the region surrounding a vehicle, by: constructing virtual box around volume containing a candidate wall-object; calculating energy-profile for the radar image within the virtual box; and applying a classification function to the energy-profile.
 15. The system of claim 14 wherein the step of applying a classification function comprises calculating at least one wall-indication parameter selected from a group consisting of: overall energy reflected from within virtual box; profile of reflected energy from within virtual box segments; number of voxels within virtual box having energy values above a threshold value; and combinations thereof.
 16. A method for detecting a two dimensional extended target in the region surrounding a vehicle, the method comprising: providing a vehicle mounted radar unit; transmitting electromagnetic radiation into the region surrounding the vehicle; receiving electromagnetic radiation reflected from an object in the region surrounding the vehicle; detecting a spectral-reflection point in reflected radiation; constructing virtual box around volume containing a candidate wall-object; calculating energy-profile for the radar image within the virtual box; applying a classification function to the energy-profile.
 17. The method of 14 wherein the step of applying a classification function comprises calculating at least one wall-indication parameter selected from a group consisting of: overall energy reflected from within virtual box; profile of reflected energy from within virtual box segments; number of voxels within virtual box having energy values above a threshold value; and combinations thereof. 